Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$203.45	10.757%	$225.3351	$225.34	$225.35	$225.30
Purchase #2	$201.39	5.213%	$211.8885	$211.89	$211.90	$211.90
Purchase #3	$124.34	6.513%	$132.4383	$132.44	$132.45	$132.40
Purchase #4	$242.64	12.748%	$273.5717	$273.57	$273.55	$273.60
Purchase #5	$84.77	9.610%	$92.9164	$92.92	$92.90	$92.90
Purchase #6	$121.40	7.523%	$130.5329	$130.53	$130.55	$130.50
Purchase #7	$223.76	4.328%	$233.4443	$233.44	$233.45	$233.40
7 purchase totals =	$1,201.75		$1,300.1272	$1,300.13	$1,300.15	$1,300.00